How we can be invincible. Placing the good in ourselves alone, is the way to suppress envy in ourselves

You can be invincible if you never enter a contest in which victory is not under your control. Beware lest, when you see some person preferred to you in honour, or possessing great power, or otherwise enjoying high repute, you are ever carried away by the external impression, and deem him happy. For if the true nature of the good is one of the things that are under our control, there is no place for either envy or jealousy; and you yourself will not wish to be a praetor, or a senator, or a consul, but a free man. Now there is but one way that leads to this, and that is to despise the things that are not under our control.